U.S. patent application number 12/154196 was filed with the patent office on 2008-11-27 for testing method for semiconductor device having ball-shaped external electrode.
This patent application is currently assigned to Toko, Inc.. Invention is credited to Toshihiko Yamazaki.
Application Number | 20080290887 12/154196 |
Document ID | / |
Family ID | 40071812 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080290887 |
Kind Code |
A1 |
Yamazaki; Toshihiko |
November 27, 2008 |
Testing method for semiconductor device having ball-shaped external
electrode
Abstract
Disclosed is a method of testing electrical characteristics of a
semiconductor device having a ball-shaped external electrode. The
method comprises preparing a plurality of cantilever-type
contactors each supported by a support plate at a given position,
and formed in such a manner that a tip thereof has a flat surface
with an arc-shaped edge in an outer peripheral region thereof, and
a cross-sectional diameter in a vicinity of the tip is greater than
a radius of the ball-shaped external electrode, and pairing the
cantilever-type contactors to provide paired two contactors. The
method includes the steps of: pressing either one of the support
plate and the semiconductor device toward the other in such a
manner that the arc-shaped edges of the paired two contactors are
brought into contact with respective ones of two surface regions of
the ball-shaped external electrode divided by an axis of the
ball-shaped external electrode passing through a middle point
between the two positions where the paired two contactors are
supported, so as to form Kelvin contacts; and further overly
driving either one of the support plate and the semiconductor
device relative to the other in such a manner that the arc-shaped
edges of the paired two contactors are slidingly moved along
respective ones of the two surface regions of the ball-shaped
external electrode to perform a wiping operation.
Inventors: |
Yamazaki; Toshihiko;
(Saitama, JP) |
Correspondence
Address: |
COHEN, PONTANI, LIEBERMAN & PAVANE LLP
551 FIFTH AVENUE, SUITE 1210
NEW YORK
NY
10176
US
|
Assignee: |
Toko, Inc.
Tokyo
JP
|
Family ID: |
40071812 |
Appl. No.: |
12/154196 |
Filed: |
May 21, 2008 |
Current U.S.
Class: |
324/754.05 ;
324/755.07 |
Current CPC
Class: |
G01R 31/2891 20130101;
G01R 1/06738 20130101; G01R 1/06727 20130101 |
Class at
Publication: |
324/762 |
International
Class: |
G01R 31/26 20060101
G01R031/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2007 |
JP |
2007-138760 |
Claims
1. A method of testing electrical characteristics of a
semiconductor device having a ball-shaped external electrode on a
rear surface thereof, based on a Kelvin contact measurement which
is performed under a condition that respective tips of paired two
contactors are in contact with said ball-shaped external electrode
in two-to-one relationship, said method comprising: preparing a
plurality of cantilever-type contactors each including a beam
portion supported by a support plate at a given position of said
support plate, and a probe portion formed in such a manner that a
tip thereof has a flat surface with an arc-shaped edge in an outer
peripheral region thereof, and a cross-sectional diameter in a
vicinity of said tip is greater than a radius of said ball-shaped
external electrode, and pairing said cantilever-type contactors to
provide said paired two contactors, wherein said method including
the steps of: (a) pressing either one of said support plate and
said semiconductor device toward the other in such a manner that
said arc-shaped edges of said paired two contactors are brought
into contact with respective ones of two surface regions of said
ball-shaped external electrode divided by an axis of said
ball-shaped external electrode passing through a middle point
between said two positions where said paired two contactors are
supported; and (b) further overly driving either one of said
support plate and said semiconductor device relative to the other
in such a manner that said arc-shaped edges of said paired two
contactors are slidingly moved along respective ones of said two
surface regions of said ball-shaped external electrode to perform a
wiping operation.
2. The method as defined in claim 1, wherein said paired two
contactors are supported by said support plate in such a manner
that said beam portions thereof are disposed in non-parallel
relation to each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to electrical characteristic
testing of a semiconductor device, such as a BGA (Ball Grid Array),
a CSP (Chip Size Package), a WLCSP (Wafer Level Chip Size Package)
or a flip chip, which has a ball-shaped external terminal.
[0003] 2. Description of the Prior Art
[0004] Heretofore, a Kelvin contact measurement has been known as a
technique for testing electrical characteristics with a high degree
of accuracy. The Kelvin contact measurement is performed under a
condition that two contactors connected to respective ones of a
sense terminal and a force terminal of a measuring apparatus are in
contact with one external electrode of a semiconductor device
(i.e., Kelvin contacts). The Kelvin contact measurement is capable
of cancelling influences of a contact resistance and a residual
resistance of a measurement cable to provide extremely high
measurement accuracy.
[0005] In an operation of testing a semiconductor device based on
the Kelvin contact measurement, a cantilever-type contactor is
commonly used. FIG. 1 shows the structure of a conventional
cantilever-type contactor. As shown in FIG. 1, the cantilever-type
contactor 11 has a beam portion 11a and a probe portion 11b. The
contactor 11 is supported by a support plate of a probe card or the
like, through one end of the beam portion 11a. The support plate is
adapted to be moved in an upward/downward direction in such a
manner as to allow the probe portion 11b to be brought into contact
with an external electrode of the semiconductor device in
conjunction with the movement so as to measure electrical
characteristics of the semiconductor device. A testing method based
on the Kelvin contact measurement using such a cantilever-type
contactor is disclosed, for example, in JP 2003-270267A.
[0006] The cantilever-type contactor has a feature of being able to
facilitate a wiping operation. Specifically, an oxide film or a
contaminant is likely to be formed or attach on a surface of the
external electrode (made of metal) and intervene between the
contactor and the external electrode, to cause difficulty in
accurately performing the measurement if nothing is done. Thus, it
is critical to perform the wiping operation, i.e., an operation of
removing the intervening substance, such as an oxide film, from the
surface of the external electrode, so as to expose the original
metal surface of the external electrode, in advance of the
measurement.
[0007] Recent years, along with complexification in configuration
of a semiconductor device for meeting needs for higher-speed
operation and larger capacity, a semiconductor device (e.g., BGA or
CSP) having a ball-shaped external electrode (hereinafter referred
to as "bump ball"), instead of conventional types, such as a lead
terminal and an electrode pad, has been increasingly used. If such
a semiconductor device having a bump ball is subjected to the
testing method using the above conventional cantilever-type
contactor, the following problems will occur.
[0008] FIG. 2 is a schematic diagram showing a contact state
between the conventional cantilever-type contactor and one bump
ball. As shown in FIG. 2, the conventional cantilever-type
contactor 11 has a tip end P which is fairly thinner and weaker
than the bump ball 13. Specifically, the bump ball 13 has a
diameter of about 100 .mu.m, whereas the tip end P of the
cantilever-type contactor 11 typically has a thickness of about 10
to 50 .mu.m. Thus, during a process of bringing the cantilever-type
contactor 11 into contact with the bump ball 13, the tip end P is
likely to be deformed. In some cases, the tip end P slips off a
surface of the bump ball 13 to preclude a stable contact with the
bump ball 13. In some cases, the tip end P deeply sticks into the
bump ball 13 to seriously damage the bump ball 13. Considering
these problems, it is difficult to use the conventional
cantilever-type contactor for testing of a semiconductor device
having a bump ball.
[0009] For this reason, a POGO pin-type contactor has been used
mainly in the electrical characteristic testing of a semiconductor
device having a bump ball. FIG. 3 shows a testing method using a
typical POGO pin-type contactor. The POGO pin-type contactor
illustrated in FIG. 3 comprises a plunger 26 and a body member 27.
A coil spring 28 is arranged inside the body member 27 in such a
manner as to allow the plunger 26 to be brought into contact with
one bump ball 23, with a spring load depending on elongation or
contraction of the coil spring 28, and electrically connected to
the bump ball 23.
[0010] However, it is hard to perform the wiping operation using
the POGO pin-type contactor illustrated in FIG. 3, and thereby it
is difficult to achieve a high-accuracy measurement. Moreover,
dusts are likely to be trapped in notches or depressions in a
measurement portion (indicated by an elliptic area in FIG. 3) of
the plunger 26, and the trapped dusts are hardly removed from the
depressions. The difficulty in removing the dusts is likely to
cause the occurrence of defects, such as contact failure, and
preclude long-term use of the contactor. In addition, in connection
with recent progress in integration of a semiconductor device, a
bump ball has been increasingly reduced in size. Thus, in an
operation of testing electrical characteristics of a semiconductor
device having such a small-sized bump ball based on the Kelvin
contact measurement, it is extremely difficult to allow two POGO
pin-type contactors to be brought into contact with one bump ball.
This makes it difficult for the POGO pin-type contactor to achieve
a high-accuracy measurement in a simple manner.
SUMMARY OF THE INVENTION
[0011] In view of the above circumstances, it is a first object of
the present invention to provide a testing method capable of
reliably achieving a wiping operation, in advance of electrical
characteristic testing of a semiconductor having a bump ball. It is
a second object of the present invention to provide a testing
method capable of reliably forming Kelvin contacts, during
electrical characteristic testing of a semiconductor having a bump
ball.
[0012] In order to achieve the above objects, the present invention
provides a method of testing electrical characteristics of a
semiconductor device having a ball-shaped external electrode. The
method comprises preparing a plurality of cantilever-type
contactors each including a beam portion supported by a support
plate at a given position of the support plate, and a probe portion
formed in such a manner that a tip thereof has a flat surface with
an arc-shaped edge in an outer peripheral region thereof, and a
cross-sectional diameter in a vicinity of the tip is greater than a
radius of the ball-shaped external electrode, and pairing the
cantilever-type contactors to provide paired two contactors. The
method includes the step of pressing either one of the support
plate and the semiconductor device toward the other in such a
manner that the arc-shaped edges of the paired two contactors are
brought into contact with respective ones of two surface regions of
the ball-shaped external electrode divided by an axis of the
ball-shaped external electrode passing through a middle point
between the two positions where the paired two contactors are
supported. The method further includes the step of further overly
driving either one of the support plate and the semiconductor
device relative to the other in such a manner that the arc-shaped
edges of the paired two contactors are slidingly moved along
respective ones of the two surface regions of the ball-shaped
external electrode to perform a wiping operation.
[0013] Specifically, in the method of testing electrical
characteristics of a semiconductor device having a ball-shaped
external electrode, according to the present invention, each of a
plurality of cantilever-type contactors has a probe portion formed
in such a manner that a tip thereof is subjected to grinding so as
to have a flat surface with an arc-shaped edge in an outer
peripheral region thereof, and a cross-sectional diameter in a
vicinity of the tip is greater than a radius of the ball-shaped
external electrode.
[0014] Then, the cantilever-type contactors are fixed to a support
plate in such a manner that paired ones of the contactors to be
brought into contact with the ball-shaped external electrode in
two-to-one relationship. Then, in response to pressing the support
plate toward the semiconductor device (or pressing the
semiconductor device toward the support plate), the paired two
contactors are brought into contact with the ball-shaped external
electrode to form Kelvin contacts. Further, in response to overly
driving the support plate (or the semiconductor device), the
arc-shaped edges of the paired two contactors perform a wiping
operation. Through the wiping operation, an original surface of the
ball-shaped external electrode (made of metal) is partially exposed
to allow the arc-shaped edges of the paired two contactors to be
electrically connected to the exposed portions.
[0015] One of the paired two contactors and the other contactor are
connected to respective ones of a sense terminal and a force
terminal to perform electrical characteristic testing of the
semiconductor device based on a Kelvin contact measurement.
[0016] As above, the method of testing electrical characteristics
of a semiconductor device having a ball-shaped external electrode,
according to the present invention, makes it possible to reliably
achieve a wiping operation so as to perform a Kelvin contact
measurement with a high degree of accuracy. In addition, the method
of the present invention allows the contactor to have enhanced
durable and longer usable period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram showing a conventional
cantilever-type contactor.
[0018] FIG. 2 is an explanatory diagram showing a contact between
the conventional cantilever-type contactor and a ball-shaped
external electrode.
[0019] FIG. 3 is an explanatory diagram showing a testing method
using a typical POGO pin-type contactor.
[0020] FIG. 4 is a side view showing a contactor for use in a
testing method of the present invention, together with a bottom
view thereof.
[0021] FIG. 5 is an explanatory front view showing a contact
between a ball-shaped external electrode and each of paired two
contactors for use in the method of the present invention.
[0022] FIG. 6 is an explanatory top view showing a wiping operation
and a contact mechanism of the paired two contactors for use in the
method of the present invention.
[0023] FIGS. 7(a) and 7(b) illustrate a wiping trace formed in the
ball-shaped external electrode after the contact with the paired
two contactors for use in the method of the present invention,
wherein FIGS. 7(a) and 7(a) are a front view and a top view of the
ball-shaped external electrode, respectively.
[0024] FIG. 8 is a schematic diagram showing one example of a
contact state during testing of a semiconductor in the method of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] With reference to the drawings, an embodiment of the present
invention will now be described. The following description about
this embodiment will be made based on one example where a
semiconductor device comprises a plurality of ball-shaped external
electrodes (hereinafter referred to as "bump balls") each formed to
have a diameter 2R of 390 .mu.m, and arranged at intervals of 800
.mu.m.
[0026] First of all, a contactor for use in a testing method of the
present invention will be described. FIG. 4 is a side view showing
the contactor for use in the testing method of the present
invention. As shown in FIG. 4, a cantilever-type contactor 1 is
used in the testing method of the present invention. The contactor
1 has a beam portion 1a and a probe portion 1b. The probe portion
1b is formed to have a sectional diameter 2r greater than a radius
R of a bump ball, in a vicinity of a tip thereof. In this
embodiment, the sectional diameter 2r is set at 280 .mu.m. The tip
of the probe portion 1b is subjected to grinding so as to have a
flat surface with an arc-shaped edge 4 formed in an outer
peripheral region (i.e., the shaded region in FIG. 4) thereof.
[0027] With reference to FIG. 5 to FIG. 7(b), a process of the
testing method of the present invention will be described below.
FIG. 5 is an explanatory front view showing a contact between the
bump ball and each of paired two contactors for use in the method
of the present invention.
[0028] The beam portion 1a of each of the paired two contactors 1
is supported by a support plate of a probe card or the like, at a
given position of the support plate. These positions are adjusted
to allow the paired two contactors to be brought into contact with
a common one of the bump balls (i.e., in two-to-one relationship),
as will be specifically described later.
[0029] In response to a pressing force applied to the support plate
toward the semiconductor device 2, the paired two contactors 1 are
gradually moved close to the semiconductor device 2. When the
pressing force is continuously applied, the respective arc-shaped
edges 4 of the paired two contactors 1 are brought into contact
with a surface of the bump ball 3. In this embodiment, a distance L
between the paired two contactors 1 is set at about 90 .mu.m.
Alternatively, the distance L may be set at any other suitable
value allowing the paired two contactors 1 to be brought into
contact with the bump ball 3 without a contact between the paired
two contactors 1. Further, instead of applying a pressing force to
the support plate, the pressing force may be applied to the
semiconductor device so as to allow the paired two contactors 1 to
be brought into contact with the bump ball 3.
[0030] The following description will be made about respective
contact positions of the paired two contactors 1 with the bump ball
3. FIG. 6 is an explanatory top view showing a wiping operation and
a contact mechanism of the paired two contactors for use in the
method of the present invention. The line A illustrated in FIG. 6
is an axis of the bump ball 3 passing through a middle point
between the two positions at which the paired two contactors 1 are
supported by the support plate. Given that the surface of the bump
ball 3 is divided into two surface regions by the axis A, the
arc-shaped edges 4 are disposed to be brought into contact with
respective ones of the two surface regions. Preferably, the paired
two contactors 1 are supported to define a certain angle
therebetween (i.e., in non-parallel relation to each other) as
shown in FIG. 6, instead of being supported in parallel relation to
each other.
[0031] In response to the pressing force applied to the support
plate toward the semiconductor device, the arc-shaped edges 4 of
the paired two contactors 1 are brought into contact with the bump
ball 3. Then, when the support plate is further overly driven, the
respective beam portions 1a of the paired two contactors 1 are
bent, and each of the arc-shaped edges 4 is moved in a longitudinal
direction of a corresponding one of the beam portions 1a. Thus,
according to an interaction between the arc-shaped edge 4 and a
corresponding one of the curved surface regions of the bump ball 3,
the arc-shaped edge 4 is slidingly moved along the surface region
of the bump ball 3 while following a locus as indicated by the
arrowed curve "t" in FIG. 6. During this movement, the surface
regions of the bump ball 3 are wiped by respective ones of the
arc-shaped edges 4 of the paired two contactors 1.
[0032] Thus, the paired two contactors 1 are electrically connected
to the bump ball 3 while wiping respective ones of the surface
regions of the bump ball 3, without a contact therebetween. In
addition, the paired two contactors 1 are brought into contact with
a common one of the bump balls 3 at different positions,
respectively. Thus, one of the paired two contactors 1 and the
other contactor can be connected to respective ones of a sense
terminal and a force terminal of a measuring apparatus to perform a
Kelvin contact measurement.
[0033] FIGS. 7(a) and 7(b) illustrate a wiping trace formed in the
bump ball after the contact with the paired two contactors. As seen
in FIG. 7(a) which is a front view of the bump ball, two wiping
traces 5 are shallowly formed in the surface of the bump ball 3.
The reason is that the sectional diameter 2r of each of the paired
two contactors 1 is set at a relatively large value allowing a
pressing force of the contactor 1 to be adequately distributed, so
that the contactor 1 can moderately wipe the bump ball 3 without
seriously damaging the bump ball 3. As seen in FIG. 7(b) which is a
top view of the bump ball, two half-moon-shaped or crescent-shaped
traces 5 are formed in a symmetrical pattern. The reason is that
each of the paired two contactors 1 is slidingly moved along the
surface region of the bump ball 3 while following a locus as
indicated by the arrowed curve "t". The difference in shape, such
as a half-moon shape and a crescent shape, arises from a difference
in pressing force of the contactor 1.
[0034] In the conventional testing method, dusts created by the
wiping operation or the like are accumulated between paired two
contactors during repetition of the testing, to cause measurement
errors. Thus, the conventional testing method is required to clean
the tips of the paired two contactors through grinding or the like.
In the testing method of the present invention, the distance
between the paired two contactors 1 is changed (in a
rightward/leftward direction in FIG. 6) in conjunction with the
wiping movement following the arrowed curve "t". This change in the
distance between the paired two contactors 1, and a smoothly curved
surface in the vicinity of the tip of each of the paired two
contactors 1, can prevent accumulation of dusts. Thus, measurement
errors due to accumulated dusts are less likely to occur even after
repetition of the testing, so that a maintenance operation, such as
grinding, may be performed only for re-forming the arc-shaped edge
of the contactor, i.e., a frequency of the maintenance operations
may be significantly reduced as compared with the conventional
testing method. The grinding is one of the negative factors causing
shortening of a usable period of the contactor. On this point, the
contactor 1 for use in the present invention has a longer usable
period than that of the conventional contactor.
[0035] FIG. 8 is a schematic diagram showing one example of a
contact state during testing of a semiconductor in the method of
the present invention. In this example, twelve contactors 1 are
fixed to a support plate while adjusting respective positions of
the contactors 1 in such a manner as to allows paired ones of the
contactors 1 to be brought into contact with a common one of six
bump balls 3 of a semiconductor 2, in a radial arrangement about a
center of the semiconductor 2. While twelve contactors 1 are used
in this example, the number of contactors may be selectively
determined depending on the number of external electrodes and/or
the need for Kelvin contacts. In response to a pressing force
applied to the support plate toward the semiconductor device, each
of the contactors 1 is brought into contact with a corresponding
one of the bump balls to form Kelvin contacts, while wiping the
bump ball in a direction from an outward side to an inward side of
the semiconductor device. This makes it possible to test electrical
characteristics of a semiconductor device having a bump ball, with
a high degree of accuracy in a simple manner.
* * * * *